I agree with SwampDonkey. Find a pen you like for weight, style, size, etc., then just get the Space Pen Refills.

I like a thick, heavy pen (easier to write with when using a wrist brace). I've received several as company promo gifts. After I'd been embarrassed enough when it stopped writing on paper with hand oils, I got a Space Pen refill and have never looked back. Much cheaper than the full pen, especially when I've lost them.

Space Pen has refills for Fisher, Cross and other brands.
http://www.spacepen.com/Public/Products/PenRefills/

Tirec