Since it's not too much money, I would just get the one from one of our vendors, that way you know it will work well, and you don't waste money experimenting with something that may cause problems down the road. Plus, it helps our vendors.
I bought a check valve from Grainger's years back with the Viton seal, etc.. and it seemed to be working ok until I realized it took waaaaaay too much vacuum for it to open up after a while. It just got gummed up pretty fast and I ended up buying one off a vendor (I think it was ATR). Their valve was bigger, had the viton seal, and opened with MUCH less vacuum, and sealed boost up perfectly, unlike the stock PCV.
I've been really happy with my catchcan, and I have the valve inline with it like others have described. I could have tried to save some $$ by trying to make my own, but the guys who made the product did the R&D on it, and I don't mind spending a bit on something that eliminated a problem I was having and saved me tons of time, which to me is worth more than saving a couple of bucks.
Billy
Montgomery Village, MD