Replacing Saucony Grid Nitrous - upgrade or refit?

Hi all,

I have been wearing Grid Nitrous since I started running a few years ago - never given me any problems. I managed to find the same pair online although they were already discontinued 18 months ago but they are now starting to wear out.

Ideally, I would simply buy another pair but I think all old stock is now gone! So the question to the more experienced - is it a simple case of knowing what model replaced them, or is tehre no such thing and I should be heading back to the shop for an assessment?

Thanks! 

quick look on sportshoes.com (see sponsored link on the right of the page) shows the nitrous as a support shoe.  A quick browse of the web site found the Fusion as another Saucony support shoe at roughly the same price as the nitrous. 

I saw that but didn't know if that was a general or specific term!