Need some help on the Mods to my Char-Griller SFB Smokin Pro

[alexhortdog95]

First off, let me say that I've been looking at the mods on here and have enjoyed looking at all of them.  I've done one thus far - the chimney mod (with the stovepiping inside).  Works like a charm. 

Now, I'd like to seal up the cracks where smoke escapes.  I went to Ace Hardware to find some high temperature sealant, but they didn't carry any.

What's the best (and preferrably, most inexpensive way) to seal up the smoking chamber (as well as the firebox)?

Forgive me if this has been asked already - I'm new to the Forums.

Thanks in advance all!