Is it possible to install a keyless entry system on a 1999 mx5 and where to purchase if it is a go.

Absolutely. Most of the better kits combine remote entry with other features. Google (Froogle is better) for Miata keyless entry kit. GoMiata, Flyin' Miata, Moss Motors, etc. may be other sources. There are plenty of kits out there. Don't scrimp. Get a good one.