You can buy microscopes on Amazon that fit your criteria:
https://smile.amazon.com/dp/B00ZAS8LH6/ref=emc_b_5_t
Detachable 5MP camera, with USB cable to laptop
40X - 2500X
$456
https://smile.amazon.com/dp/B00AEJ9FJ4/ref=emc_b_5_t
Built in 3MP camera, with USB cable to laptop
40X - 2500X
$442