I could use some advice about getting a suit on somewhat short notice because I am a fool

I’m in a bit of a self-made pickle and could use some pointers for how to get out of it.

I’ve been invited to a Japanese friend’s wedding, which is to take place in two and a half weeks. I tried on my suit today, and it really doesn’t fit. The last time I wore it was several years ago and I’ve lost some weight, and in retrospect it probably never fit well to begin with. At the very least the jacket is too large/long and the waist on the pants is perhaps 12cm too large.

I think the best solution is to buy a new suit. In parallel I plan to examine the feasibility of getting my old one tailored, but I’d rather that be a backup plan because I really am dubious it's salvageable.

Where can I get a suit (and shirt) that will fit with some degree of confidence? I’m willing to pay a premium for a “rush” fee, so I can get it ASAP and have some peace of mind. I just want a standard black two piece suit and a white shirt.

I am not looking for anything fancy. I just want it to fit well and be reasonably respectably dressed for a Japanese wedding ceremony, and I probably won’t wear it again for a while. Unfortunately from some of what I’ve read “fit well” seems like it might be a tall ask at this point if that requires several revisions, so I’m definitely willing to settle for “not bad”.

My proportions aren’t extreme in Japan – I wear an M or L from uniqlo depending on the piece, with the exception of having somewhat short legs and arms.

I'd prefer to keep things under 5 to 10man if possible, but if that's not realistic I can make it work.

I really have no experience buying clothes like this, so I'm at a loss about how to approach this problem. Should I just go to one store and commit to whatever the sales person tries to sell me and hope I get lucky? Do I need to shop around? This is a good amount of money to spend, but at this point do I have no choice but just commit before knowing what the final product will look like?

So, if I could get pointers to specific shops that are likely to meet my needs (Aoyama? AOKI? Suits Company? etc), how to actually do the shopping and especially stories from anyone that’s been in a similar situation I’d greatly appreciate it. Thanks!