Extreme Ghostbusters Toy line was created by Trendmasters from 1997. It was mostly related to the Extreme Ghostbusters. Interestingly enough, Samhain got a toy in the lineup but Garrett Miller didn't get a figure made.
List of Toys
Trendmasters did a prototype of the Garrett Miller figure. Garrett's wheelchair here is completely modified from what is seen on Extreme Ghostbusters, and indeed would not fit in the Ecto-1 Cruiser. His hair is also a lighter shade then his actual animated look, which was often the case with any prototype Trendmasters made before the final colors were established.