Pictures will haelp you get answers.

Cheapest and looking good are not the same thing. You will need custom if you want to fill the alcove. Or downsize to a freestanding 48”.

It’s made of pressed wood (that’s crumbling) and the sink bowls are shaped like seashells currently. Unfortunately it’s gotta go.

Two vanity cabinets from Home Depot or similar, or an actual cabinet seller. You might find them in 33" width (or 32.5").

Custom laminate (formica) countertop with drop in sinks.

Find a 60" vanity on Marketplace or somewhere similar. Use 3" of fillers on each side. Paint.

Laminate counter. Easy enough to fabricate yourself, You can order sheet laminate at Home Depot or Lowe's. Or order a custom countertop from Menard's if you have Menard's in your area.

If you want to be really cheap, you can save and reuse the counter/sinks. They are almost old enough to be cute again. :)