I have a MAX Keyboard 8 switch sampler - I'd only recommend that one if you're at all interested in MX Clear, White or Grey. You could also purchase the MAX 4 switch tester & buy individual switches (for instance, clear, white or grey) to test them out. I'm sure that isn't cost effective, but you're able to do that if you like. MAX switch samplers come unassembled so you need to install each switch in to the base yourself. This lets you be in charge of your switch orientation and lets you swap switches if you like in the future.
I believe you can also do that with the WASD switch tester but I'm not 100% sure because I do not own one.