Rubicon Express part 1822. Almost the exact same thing, but you won't be getting old used parts.
http://www.rubiconexpress.com/Products.aspx?Cn=328&Pn=1809&XnPath=320,321,328&Vid=903FC02626628
Any RE vendor can help you. I suggest Loose-Nuts-Enterprises (naxja vendor) based on prior experience, but you can use the vendor of your choice.
Otherwise, you can go to
www.car-part.com, enter in a YJ year, jeep, wrangler, rear drive shaft, and scroll to the lowest price. Start calling the vendors and seeing who will sell just the slip yoke cheap, I bet you can get one for $40 delivered. Here are the first few I would call based on the results I got searching:
House of Auto Parts, Inc. USA-MI(River-Rouge) 1-800-241-1125
Boughton's Auto Salvage, Inc. USA-PA(Susquehanna) 1-800-779-3925
Harris Truck Parts USA-CO(Colorado-Springs) 1-800-441-5839
Kress Auto Recyclers USA-PA(West-Hazleton) 1-570-454-7211
Dont' say "YJ", you will confuse them. Tell them you need a rear driveshaft yoke at the transfer case end, for a 1990 jeep wrangler. auto/manual/4cyl/6cyl doesnt matter. If the first guy won't do $45 shipped, politely thank him and call the next guy. 15 minutes on the phone will always get you the best deal that is to be had.
-C
i used to live in toledo and that was my yard of choice.... and when i wrecked my racing bimmer she went there to sleep forever more 
