Plasma to the eyes!
No, seriously: Have you been to Vault City and Gecko yet? You can get a fair bit of money in those places, it should be enough to get you above $2000 so you can go back and get the car. There's no way to get to 2k when you first come across the car (unless you don't pay for Sulik and Vic and have done a lot of stealing).
But yes, merchants respawn their money in 2-4 days. The only problem is that San Fransisco is the only place where large amounts (thousands) are spawned, everywhere else its like 300 at the most, and SF is the only place where it consistently spawns.