I went to the exhaust shop, and he said it isn't really possible, due to it not being able to fit or something like that.

I know most fake twin tips look ****, but I have a TS50 back, and want to fill the exhaust hole accordingly. I think the fake TS50 twin tip would look good.

Is there any alternatives? Possibly an online place where I can check out some aftermarket tips?

Can anyone offer some advice?

get twin 3" or 3.5" tips. That'll fill it