Hi Roger,
Seeing that this one has not seen a response in 24 hours I thought I'd chime in. First, welcome to TY. There is an amazing amount of useful info in this section that will address most anything that might come up on your MP. As the mods say ... search is your friend.
Regards the wind shield bag I know nothing, have never seen or heard of such a beast for the MP. But you got me thinking because I take a fair bit of gear with me whenever I'm out and there is a lot of space out front. Next time I'm in town I'm going to take a look at those larger fanny packs that skiers use. I could either cut off the belt to make it a dedicated W/S bag or leave the straps on to make it multi-purpose(pun intended) and wear it as intended when I leave the sled, either to go exploring on foot or when I'm walking home which hasn't happened yet but I have been rescued a few times. Twice stuck in overflow and once through the ice at the shoreline.
Again, welcome.