Ordered this fill probe for my FX Bobcat MK2, and received it last week. Yes, I know it has two more O-rings than the fill probe that comes with the gun, but it works perfectly. Stainless steel, fill probe on one end, male foster on the other. Works just like the original. It actually seems beefier and more rugged than the stock fill probe. Comes with two extra sets of O-rings (mine came with 8 extra, not 6 like shown in the photo). For $15.99 with free shipping and no tax, can't hurt to have a spare fill probe for your FX! They (jimmyfan1981) also have fill probes for Edgun and Kalibrgun. The only downside is that it took about two weeks to be shipped from China.
http://r.ebay.com/XrZGt6
http://r.ebay.com/XrZGt6