I know right where you're at.  Skip the guy in Brookfield and go to that Fleet Farm or Farm & Fleet or whatever the heck they call it - the one on 18 behind that PDQ.  They've got 'em.  I bought mine there.  Home Depot should have them too, but they're a tad more expensive.  Otherwise, you can go down to Hwy 100 and between Northern Tool and HOBO there's a Graingers (electrical supply house).  (That's right off the freeway on Hwy 100)
You won't find wire easily available around here in 18-22 gauge except for at Radio Shack.  Grainger SHOULD have some available, but they seem to sell out of it pretty quickly.  You'd think they stock more, but they do a lot more business in mail-order.
If you still want, here's the two distributors for our area and I haven't dealt with them, so I don't know which to tell you (although ponyboy has better prices on buttons/joys than Happs).  From the Happs book:
Outside Sales Representative
Eric Skowlund
Tel:  800-511-1796 Ext 470
Office:  262-677-9125
Cell:  847-867-0628
E-mail:  eric.skowlund@happcontrols.com
Inside Sales Representative
Dan Trivits
Tel:  800-511-1796 Ext 103
E-mail:  dan.trivits@happcontrols.com