Re: where to buy 3m 5200
I've seen it at home depot, sometimes Menards, and of course west marine.
5200 is the permanent stuff, 4200 is less permanent, fast cure 5200 is the fast curing stuff (obviously).
I get mine at Home Depot for about $8 a tube (the caulk tube size, not the squeeze tube).
Alternatively you can use PL Concrete crack and mortar sealer (this is NOT the same thing as the PL Premium adhesive). Other than the fact that it's a light gray color (concrete color) it's the same ingredients as 3m 5200, but since it doesn't have "marine" written on the package it's only about $3 a tube.
I've used it for a few years... once dry it's just as annoying and difficult to remove as 5200 is.
Erik