Reddit mentions of OASIS #64225 Turtle Ramp - Medium 12-Inch by 6-1/2-Inch by 3-1/4-Inch

I think I see what you mean. Turtles are actually really good at climbing, and they can usually climb up onto their basking platform without needing to touch the bottom of the tank. There are ramps that have a longer segment that goes into the water so the turtle can sort of wade up onto the basking platform, like this one: https://www.amazon.com/OASIS-64225-Turtle-Ramp-12-Inch/dp/B0002DIM9G/ref=pd_lpo_vtph_199_tr_t_2?_encoding=UTF8&psc=1&refRID=5DZYNJXZ16TSNW5D8V31

Filter size depends on the turtle and tank size. For example if your turtle is 4 inches long (down the length of the shell not including head and tail), I'd recommend a 40 gal tank with a filter rated for an 80-100 gal tank. You want to look at the tank size recommendations for filters ('tanks up to 100 gal', for example) instead of the 'GPH'/gallons per hour ratings. Sunsun is a cheaper brand that a lot of people on this sub use, example here: https://www.amazon.com/Sunsun-Canister-Filter-264gph-HW304-525gph/dp/B07DLCXNPK/ref=sr_1_3?s=pet-supplies&ie=UTF8&qid=1541686346&sr=1-3&keywords=sunsun%2Bfilter%2Bcanister&th=1

Eheim and Fluval are also good filter brands, although they are more expensive.