...eBay?

There's no 'proper' retailers of issued CADPAT kit...mostly because it's hard to get in any quantity. Check with Army Issue though, he might have some.

Cant you just get some cadpat fabric and stick it on? Carefully shape it and glue it.

If you want to fit the issued cadpat cover on a Mich, be sure that it does not have the pads inside and it's using the suspention. As the issued cadpat cover use plastic tabs that stick with friction inside a circular ring inside the helmet suspension.

I tried those cover on a old issued PASGT and it was a very loose fit. The elastic band helped keep it in place.

Gallet helmet (Canadian version of the MICH) are easy to find cheap if you look around. A lot of people have some to sell. Ask the right persone.
I got mine almost brand new with all covers, nets, and new suspention for 75$.
Don't despare.