I don't think that's worth doing. From memory they are all 1/4" BSF and apart from the two cranked ones in the wheel hubs (which I never use anyway), I'm quite sure that all the rest of mine are straight.

I have to unscrew the steering damper knob to get the grease gun on the nipple on the top yoke. Both the brake cams on both my bikes have screw in nipples Ron

PS. plenty on ebay. Pack of 10 for 6 quid looks good.

http://www.ebay.co.uk/itm/Grease-Nipple-Fitting-1-4-X-26-BSF-10-UK-manufacture-free-1st-UK-postage-/232226520994?hash=item3611c77fa2:m:myYNS1gQdhfgl_tLp2mtciA

email (option): ronpier@talk21.com