In Europe we can't get MSU here most as far as I know use Rainmix from Akerne.
You could use a hydroponic fertilizer, the only main things to watch out for is that it has all the nutrients it should have which shouldn't be an issue with most good quality fertilizers but also that it doesn't contain any Urea, a cheap form of Nitrogen which can't be absorbed as well by plants.
I used to feed a fertilizer that had 1/3 urea so not a lot but I think switching to 0% Urea has made a difference.
here is a good article on the matter:
Orchid Fertilizer Myths - Grow More Flowers - Garden Myths