Damn, you’re not one of those “planning ahead” type, eh? I hate to say this, but for that price range and time frame, you’re probably left with a lot of “not good” options. I don’t know many places that are willing to turn around alterations in 3-4 days.
If you’re on the trim side and have a Zara near you, then that’s an option. Their suits fall under your price range and you could either go the cotton route or try to find one that’s 100% wool. Definitely avoid their polyester-wool blends. Don’t expect the best construction though. Also, I don’t think they do alterations. The upside is that they sell pants and jackets separately.
You could also stop at a Macy’s and check out their Tommy Hilfiger “trim fit” line, also sold in separates. Most Macy’s do alterations and you could ask them to maybe put a rush on it.
Outside of that, in that price range, you might be relegated to *shudder* Men’s Warehouse or Jos. A. Bank, both of which I can’t recommend. If you do go this route, insist on something slimmer and also 100% wool (or cotton).
If you had more time, then I’d point you immediately toward Lands’ End’s tailored fit fine, which you can buy in separates. They’d need alterations though, but the upside is that LE often has 25-30% off sales if you subscribe to their email list. I have two LE suits and they’re decent beginners/workhorse suits once tailored.
If you’re willing to spend a little bit more money, then I’d recommend trying to hit up a Brooks Brothers or J.Crew or similar-tiered retailer.
In this case, your options are limited and you’re either going to end up spending more money than you want to get something decent or spending money on something that’s overpriced for the quality.