Model Kits: Plastic grenades.
 

http://www.hobbyasia.com/products.ph...sID=228&page=0

This page sells three things I'm interested in, the MKII's, the M18's and the potato mashers.

Think they'd get past customs?

They wouldn't be assembled, so you should stand a good chance of getting them through. The thing is, there is no law against "Replica Explosives" (unless you're at an airport and/or misusing it), but CBSA has the power to seize them and make it difficult for you. Or you could get a reasonable person and it'd all be fine.