There's the ReelMagic basic packer which is probably as realistic as you're going to get in that price range for $80 (£50), but there's also shipping costs $40 (£25), which brings that up to £75, but there's every chance that customs are going to stop it and charge you a stupid amount as well. I tried working out how much that could be for you but I can't work out what category it would come under and different things tend to get charged at different rates. I do know that Royal Mail have a £8 handling fee, and a £35 watch incurred a total of £13 fee, so plan for it to be more than that if I was you encase they do stop it.
I can check for you if you'd like, I've got the package from my watch but it's in my bike still and I don't fancy going outside right now, but I'm pretty sure it didn't say anything on the sticker customs put on it about what was in it incase that concerns you if you might have to pick it up from a post office. I don't know whether or not ReelMagic themselves are discrete or not though, but being quite a popular company - and not one that specialises in prosthetics/packers I'd imagine they are and that someone else on here will be able to answer you.