How about a
Paddle Board - although I think these are quite hard to carry around aswell.
The longer and thicker and wider the board, the more stable they are and easier to paddle...
I found this on ebay:
This one is probably too small:
http://cgi.ebay.com/Quiet-Flight-Use...item43a8d96c73
This is probably the style you want... but not at this price:
http://cgi.ebay.com/8-Bud-Gardner-Su...item48322bedc3
This one is again probably too small...
http://cgi.ebay.com/Bic-Surfboard-73...item2c5e8651fc
This is probably ideal, as its softtop, bouyant, long, wide, thick.. in fact its perfect:
http://cgi.ebay.com/New-Triple-X-Sup...faultDomain_0&hash=item3f0bf9e85f
On another note... I might start importing surfboards into Florida... they are well expensive over there