Collecting hot wheels

My son is becoming interested in some hobbies I had as a kid, so we've begun keeping an eye for stores whenever/whereever we go shopping. Its really cute.

Obviously Tomica is the king here, but I've exhausted all the typical shops around us, but theres just not much stock or variety.

'Warehouse' in Shimokitazawa is good, but is there any other stores with a large hot wheels selection, or focused on hot wheels? Tokyo/Saitama areas okay.

(I've dont your typical kids stores, toys r us, donki, etc.)

by philipjfry__