IPS screen mod for your GB, these are usually not too costly iirc ($60 USD?)
GBA SP (AGS 001 is frontlit and AGS 101 is backlit), around the same budget for the former, the latter is more coveted and expensive. (EDIT - initial mistake, the GBA is not front/backlit)
Open source cartreader to dump your carts and saves (and play ROMs wherever you want) - no idea about the budget tbh
Analogue Pocket, it's great but very likely overkill if all you want to do is play some GB games ($220 USD)
Depending on how comfortable you are with downloading ROMs (and how ethical you feel that is, given you already have the games), you could just do that without spending a penny since GB games have been preserved and are easily accessible.
There's also a handful of other options (GameCube GB Player, SNES Super GameBoy, etc), but that's likely more consoles and accessories for you to purchase so I didn't mention those in detail.