I love Underrail but one of the worst parts of playing the game is looking for a very specific crafting item like a Grenade launcher scope or a Rapid reloader, for infusion one way this issue could be solved while still keeping the randomness of traders would be the ability to request a trader find a specified part which they could give you after there next shipment. For components like frames that have a quality to them the quality you get could be dependent on the trader stock as well as how much money you spend on the reservation.
To balance this I would say to order a component for the next shipment you would have to spend an increased price which would be a percentage of the components base sell rate. This price could be dependent on difficulty with a rate like:
Easy: 150% base sell price
Normal: 200% base sell price
Hard: 250% base sell price
Dominating: 300% base sell price
I think this addition would make the game way less grindy and make AFKing for specific parts way less likely
