the mcmaster parts keeping going up... unless you are doing like 6 fittings its probably not worth it to do the full-out hexnut weldless fitting yourself, but here is what I used..
WELDLESS CONVERSION (FOR KEG)
Get parts from wwww.mcmaster.com
McMaster Part No. Description Cost
4464K214 Stainless full coupling, 1/2" pipe size, $3.42
4830K171 Stainless Steel 1/2" Close Nipple, Fully Threaded, $1.69
98126A797 Stainless Steel Shim(sold only as a pack of 10 @ $10.38 ) $1.04
9396K32 Silicone O-Ring (sold only as a pack of 50 @ $14.53)* $0.29 (x2)
4429K124 1/2" Locknut, Brass (with groove for o-ring) $1.30
4190K22 1/2" Brass Ball Valve, Full Port $6.89
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Total Cost $14.92
http://www.antiochsudsuckers.com/tom/DIYweldlessfittings.htm