What I did was...found out that my aftermarket center caps don't fit

3rd and 4th Gen I believe have the same bore diameter, but there’s a groove inside the bore (for the locking clips), and it’s location varies between the two gens.

when I bought some cheap, Gen 3 E-Bay caps, purported to be genuine Toyota (they definitely weren’t), they wouldn’t sit properly. Comparing them to genuine (our 2010 CDN Touring came with 17” rims, with the centre caps), I saw the E-Bay caps had slight protrusions on the backside of the outer flange. With a little Dremel work I was able to get them to fit.

It’s not just the bore diameter; there’s lots of factors. I would start by researching the genuine Toyota part numbers, search for that. Listing for knock-off caps may mention being compatible with that part number. Also check the price for genuine at dealership parts departments, and/or online dealerships too, though they’ll likely be pricey.

Toyota USA parts website is a mess now (by design?); the dead-simple way to find out the correct part no would be to phone a parts dealership. And they’ll be able to sell you the correct, properly fitting cap, albeit more costly.

 

I purchased Toyota part # 42603-52170 from Amazon and they fit my 2021 perfectly.

 

Aftermarket ones I got fit fine

 

I have a 2017 Prius Prime. I just bought it used. I went to the local Pull-Apart and spent 30 minutes picking through a bucket to find what I wanted. They charged me $2 to get in and could have cared less on what caps I took home. I found that for the original equipment without the wheel covers, the Nissan caps were a good fit, overly abundant and best of all Free.

Shout out to my local Pull-A-Part, (Sam's) Linder's in Worcester MA