We have a flush-pro on our boat that we got from skidim, it cost all in £73 from the USA thats including delivery, import tax etc. make sure you use the code CCFAN to get your 10% discount!! or as it a mastercraft try one of the other partner sites:
Daily_Encouragement For You
Flush Kits-Discount Inboard Marine
It normaly takes a 7 days to arrive from skidim. If you just go for the standard one with no through hull its only £60 all in.
ps. please no buying from USA bashing as i do buy 90% of my stuff from local suppliers but the mark up on these was crazy!
Cheers
Rossl