I have the large snoozer scalloped ramp, it's great. Amazon has it for $108.
https://www.amazon.com/dp/B006QC1SAW..._xjpKub0VHD40H
It's one of the most expensive pet things I've bought, but it's way cheaper than an injured dog. I chose it because not many pet steps were tall enough and most would've been hard for a tiny puppy to use. Lola was even able to use them without a problem the day after she was spayed.