Here is a recent thread from the T-B-N archive discussing aftermarket FELs:
http://www.tractorbynet.com/forums/kubota-owning-operating/293894-adding-fel-my-l3200-opinions.html
Unfortunately, purchased separate from the tractor, at a later date, an FEL comes at a high price.
In most peoples opinion here on T-B-N, including mine, an FEL is the single most useful tractor option.
The current Kubota B's have a loader valve as factory standard equipment, hence adding an FEL is easy. I cannot speak to a 2005 vintage
B2630.....a call to your Kubota dealer should get you the answer, or someone here will provide the answer.
You need either R1 Ag Tires, or R4 Industrial Tires on the tractor to push an FEL: not enough traction with Turf Tires. Four Wheel Drive recommended.
Used loaders, in good condition, unsprung, are few and far between.
Create searches on Tractorhouse.com and eBay for the FEL model you want, within 200 miles of where you live, with e-mail notification, and see what shows up. You might be lucky.
Also consider a three point hitch mounted
Scoop Pan. My local Tractor Supply Co. always has house brand "Countyline" scoop pans in inventory. There are YouTube videos of Scoop Pans at work. Search YouTube for TRACTOR SCOOP PAN.
SCOOP PAN LINKS:
Tractor 3 Point Hitch Scoop Pan
http://www.tractorbynet.com/forums/owning-operating/259522-scoop-pans-they-worth-having.html
(You can buy a new Kubota B3300SU tractor/loader package for $18,000.)