I was going for having it look just like a highway sign, with the exception of the Mets script, of course. I even found the font that the highway signs use!
How about "Grand Central Mets"? The 7-Line has co-opted the name of the subway that goes to Shea, I mean, Citi. We could do the same with the highway that goes there. It also suggests that the site is a hub of activity.
I'm noticing that the Cubs site (North Side Baseball) and the Marlins site (Fish on First) does not incorporate the team name:
About DiamondCentric - DiamondCentric
DIAMONDCENTRIC.NET
And the sites for the Blue Jays (Jays Centre) and Red Sox (Talk Sox) only include a partial team name. So the question becomes, how critical is it that the site include the word "Mets"? Or could we call it "Flushing Baseball" or "Who's on Third?"
Or break the 99 ceiling and have three-digit numbers. If two of the digits are 1 (the narrowest number!) they should be able to fit three digits on the jersey.