So I've been running around for two hours looking for my last suit expansion (currently have 99/100) and have no idea where it is.

I have the observatory data for every planet, including pirate homeworld, and checked the maps about ten times for anything I might have missed. I have everything from the Valhalla (including the one in the elevator) and have the three upgrades from Bryo's ice place.

I know its a missile expansion because I only have 250 missiles max which is 49/50 missile expansions.

Does anyone know where the last pickup could possibly be???

Well.. there are 50 possible locations where it could be..
Try looking up an official guide.. Maybe you may find an online one. Follow where it tells you where to go for each pickup.

Have you checked the Valhala, there's a few expansions there and I don't think they get marked. I'm not sure where all of them are but there's one in the floor of the medical lab, one in the first elevator shaft and one in the ventilation shaft. I think there's more but if none of those sound familiar check it out.

I found it!

Thanks for the help guys it turned out to be in the Valhalla afterall