Striders in Grandville probably has the best selection on the west side. Gazelle Sports and Cross Country Cycle (Holland) both have a handful of items too.
Ironically, I was at both Striders and Gazelle this week, looking for tri shorts. Striders may have a slightly larger selection, but they both carried TYR as the main brand. IIRC, both places only had 1 or 2 tri suits. Another option would be any of the Village Bike stores.