You can make your own. I bought the following from McMaster Carr:
1) 98861A550 Metric Class 4.6 Plain Steel Threaded Rod, M14 Size,
300MM Length, 1.50MM Pitch, Fine Thread ($21.22)
2) 91415A255 Metric Zinc-Plated Steel Fine Thread Hex Nut, Class 8,
M14 Screw Size, 1.5MM Pitch, 22MM W, 11MM H, packs of 25 ($10.23)
3 91100A240 Plain Steel Flat Washer, M14 Screw Size, 44MM OD, 3MM
Thickness, packs of 25 ($6.90)
If your radiator is still in you will have to trim a few inches off the threaded rod. Otherwise just thread it in, stack the washers (I used the thrust bearing from a generic installer I already had) and run one of the nuts in. Worked like a charm. I would recommend the kit TJKJ posted if you don't already have one. That is a good price. My issue was all I needed was the one lousy extension since I already had a decent OTC kit. I tried to buy just the extension but no luck.