hey guys I just pick up a tamiya leopard A4 and i wanted to know were to get the best addon for this kit thanks

Have a look around here:

http://www.onepointed.com/dan/model/

It's the best one stop point for all your aftermarket leopard questions

W

Most accessible aftermarket products are the photoetch sets by Eduard. Some are designed for the Italeri/Revell kit, but can be used on Tamiya's without any significant problem. The Tamiya kit has chunkier details than Italeri's (in the late 1970's Italeri had actually moved ahead of Tamiya in tooling quality) and the engine deck screens are molded as solid, so you'll need to carve those out and thin the edges so you can add the photoetch screens.
There are German made aftermarket sets as well for the Leopard 1 family, but they tend to be expensive and hard to track down.