If you’re looking for an NVidia option in a laptop format you’re very limited with Apple laptops as it’s only the highest spec 15" MacBook Pro that offers an Nvidia option and they’re more than double the price of the base model (unfortunately there is no way to upgrade Apple laptop GPU units as they are hardwired into the control board). However I will say that with Apple laptops if you can afford to buy the premium options the laptop will last you far longer. I recently passed on a 15" Macbook Pro from 2006 to a family member (2.6 Ghz dual core with 4gb memory) and they use the Rhino beta without any problems. You pay an awful lot for the final 25% of performance but you also pay for protection against early obsolescence.
You can of course go for one of the the non Nvidia models. I own the latest MacBook Air (Intel powered GPU) and that runs Rhino perfectly. I wouldn’t use the Air for rendering tasks (beyond preview renders) but that isn’t the point of the Air.
Your have three other options here that spring to mind:
1.) Search out the latest “hackintosh compatible laptop” options that are available to you. Be careful here though as you really need to know what you’re doing.
2.) Buy second hand hardware from a few years ago that meets your specification for Nvidia hardware
3.) Buy a reconditioned unit direct from Apple that has the Nvidia option. This would be my recommended option as it will save you a good deal plus you get all your standard warranty/support options of buying direct from Apple.
Hope this helps.