I bought them off of Amazon in a set. They're kinda pricey for what they are, but they have a lot of good details. Shipping was a pain though, as they came from Japan so it took about a month and a half before they got to me.

Link to the Amazon listing: https://www.amazon.com/Subaru-Impreza-Concept-Test-japan/dp/B001J957V8/ref=mp_s_a_1_10?keywords=tomica+subaru&qid=1552479606&s=gateway&sr=8-10