I did a quick search on McMaster, this is for round, I know they have Hex as well.
Steel Zinc-Plated 10-32 3/4" 6" 6516K51 $6.46
Steel Zinc-Plated 10-32 3/4" 12" 6516K52 7.83
Steel Zinc-Plated 1/4"-28 1" 6" 6516K53 6.71
Steel Zinc-Plated 1/4"-28 1" 12" 6516K54 9.15
Steel Zinc-Plated 1/4"-28 1" 18" 6516K55 8.51
Steel Zinc-Plated 5/16"-24 1-1/4" 6" 6516K56 6.91
Steel Zinc-Plated 5/16"-24 1-1/4" 12" 6516K57 8.26
Steel Zinc-Plated 5/16"-24 1-1/4" 18" 6516K58 12.05
Steel Zinc-Plated 5/16"-24 1-1/4" 24" 6516K59 10.17
Aluminum Plain 3/8"-24 1-1/4" 6" 6516K61 6.91
Aluminum Plain 3/8"-24 1-1/4" 12" 6516K62 7.83
Aluminum Plain 3/8"-24 1-1/4" 18" 6516K63 8.71
Aluminum Plain 3/8"-24 1-1/4" 24" 6516K64 9.63
Aluminum Plain 3/8"-24 1-1/4" 30" 6516K65 10.51
Aluminum Plain 7/16"-20 1-3/8" 6" 6516K66 7.17
Aluminum Plain 7/16"-20 1-3/8" 12" 6516K67 8.20
Aluminum Plain 7/16"-20 1-3/8" 18" 6516K68 9.31
Aluminum Plain 7/16"-20 1-3/8" 24" 6516K69 10.17
Aluminum Plain 7/16"-20 1-3/8" 30" 6516K71 11.51
Aluminum Plain 7/16"-20 1-3/8" 36" 6516K72 12.57
Aluminum Plain 1/2"-20 1-1/2" 6" 6516K73 7.60
Aluminum Plain 1/2"-20 1-1/2" 12" 6516K74 9.17
Aluminum Plain 1/2"-20 1-1/2" 18" 6516K75 10.37
Aluminum Plain 1/2"-20 1-1/2" 24" 6516K76 11.97
Aluminum Plain 1/2"-20 1-1/2" 30" 6516K77 13.17
Aluminum Plain 1/2"-20 1-1/2" 36" 6516K78 14.74
Aluminum Plain 5/8"-18 1-5/8" 12" 6516K79 10.77
Aluminum Plain 5/8"-18 1-5/8" 18" 6516K81 12.94
Aluminum Plain 5/8"-18 1-5/8" 24" 6516K82 15.11
Aluminum Plain 5/8"-18 1-5/8" 30" 6516K83 17.29
Aluminum Plain 5/8"-18 1-5/8" 36" 6516K84 19.49
Aluminum Plain 3/4"-16 1-3/4" 18" 6516K85 15.74
Aluminum Plain 3/4"-16 1-3/4" 24" 6516K86 18.80
Aluminum Plain 3/4"-16 1-3/4" 30" 6516K87 25.06
Aluminum Plain 3/4"-16 1-3/4" 36" 6516K88 25.57
Another option would be to just get a link tube and chop it in half.
http://www.hrpworld.com/index.cfm?form_ ... on=product
http://www.hrpworld.com/index.cfm?form_ ... on=product
here's another option from mcmaster, a Connecting nut.
Grade 5 3/8"-24 9/16" 17/32" Not Rated 90565A320
$3.41 per Pack of 25
Grade 8 7/16"-20 5/8" 39/64" Not Rated 90565A325
6.45 per Pack of 25
Grade 8 1/2"-20 3/4" 11/16" Not Rated 90565A330
8.13 per Pack of 25
Grade 8 9/16"-18 7/8" 49/64" Not Rated 90565A333
3.71 per Pack of 10
Grade 8 5/8"-18 15/16" 27/32" Not Rated 90565A335
4.65 per Pack of 10
Grade 8 3/4"-16 1-1/8" 1" Not Rated 90565A340
7.60 per Pack of 10
Grade 8 7/8"-14 1-5/16" 1-5/32" Not Rated 90565A345
5.73 per Pack of 5
Grade 8 1"-14 1-7/16" 1-5/16" Not Rated 90565A350
8.39 per Pack of 5
Grade 8 1-1/4"-12 1-13/16" 1-5/8" Not Rated 90565A355
5.54 per Pack of 1
Grade 8 1-1/2"-12 2-3/16" 2" Not Rated 90565A061
20.16 per Pack of 1
Not Rated 1/4"-20 1/2" 7/8" American Society for Testing and Materials (ASTM) 90654A305 1-9 Each
10 or more
35.15 Each
29.87 Each
Not Rated 3/8"-16 11/16" 1-3/4" American Society for Testing and Materials (ASTM) 90654A311 1-9 Each
10 or more
29.44 Each
24.92 Each
Not Rated 1/2"-13 7/8" 1-3/4" American Society for Testing and Materials (ASTM) 90654A317 1-9 Each
10 or more
31.09 Each
26.42 Each
Not Rated 5/8"-11 1-1/16" 2-1/8" American Society for Testing and Materials (ASTM) 90654A323 1-9 Each
10 or more
33.69 Each
28.63 Each
Not Rated 3/4"-10 1-1/4" 2-1/4" American Society for Testing and Materials (ASTM) 90654A329 1-9 Each
10 or more
35.31 Each
29.99 Each
Not Rated 7/8"-9 1-7/16" 2-1/2" American Society for Testing and Materials (ASTM) 90654A334 1-9 Each
10 or more
36.26 Each
30.81 Each
Not Rated 1"-8 1-5/8" 2-3/4" American Society for Testing and Materials (ASTM) 90654A340 1-9 Each
10 or more
46.24 Each
39.30 Each
Not Rated 1-1/4"-7 2" 3" American Society for Testing and Materials (ASTM) 90654A346 1-9 Each
10 or more
53.94 Each
45.84 Each
Not Rated 1-1/2"-6 2-3/8" 3-1/2" American Society for Testing and Materials (ASTM) 90654A351 1-9 Each
10 or more
62.55 Each
53.16 Each