ooo, you've hit a nerve with the would be pro's on here, the one's who still wear plus 2's and use hickory and feathery balls, they don't like anything new such as belly putters. The fact that they are perfectly legal to use means nothing.
Seriously most pro's will not carry them as they do not know how long they will be on the shelf and are after quck turn arounds from pop'n' mars bars. Ag should have them as well as a lot of off course stores. Failing that check Ebay you may get one at a throw away price.
Don't mind the hickory swingers, I like you couldn't find one for ages then a couple of weeks ago one appeared in the pro shop rack (belly putter) all be it a cheapo one (£34)I thought at that price I'd risk a punt and I'm glad I did. From about 10 feet my puttings much improved on long puts the belly putter -for me anyway- feels a bit ungainly and so far no better than the standard putter I was using, but I'm sure that will improve with a bit more practice.
you can normally pick up clubs at a decent price and they have a returns policy that you can get a refund if you decide it's not for you within a certain time period.
Build your own.
Get an off cut of plastic conduit. A two way double clamp. And a bikes handlebar grip. A bit of Blue Peter glue.
Bish bash bosh
Bobs your auntie