You can get a used ECWCS Gen2 goretex parka for under $100 if you shop around (M81 or DCU), and a newer Gen3 in MC for about $200.
They have no liners and by themselves aren't as warm as a softshell (which does have a minimal liner), although they do keep moisture in more when they're dry.
Another alternative is to get a lightweight hiking rainjacket: dark grey-green/FG style colors aren't uncommon, or if you really want to preserve your camo (and maybe protect the expensive jacket from damage) you can wear it UNDER your combat shirt.
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