The best keypad you'll get at best buy is probably a $10-$20 membrane keypad but that's even if your best buy has it in-store. Idk what you're budget is or if you want a full keypad, a 2-key keypad, etc.
However, there are plenty of cheap keypads on aliexpress (quality will vary, I'd check out the most bought and make your judgment after looking at the pros and cons that each of the keypads has.)
On Amazon, I'd pick the Motospeed K2 hot-swappable for $16 as it comes with switches other than Outemu switches; from the reviews, it looks like the K2 has Kailh speed bronze switches (which means it will support most other switches, the PCB looks like will support 5-pin switches, but I can't confirm. The only problem about the K2 is the keycaps, I hear the keycaps are pretty bad.
The Sim Pad Nano is $27 and is almost exactly like the K2, but there are many more reviews on it and it will come with quality keycaps that will last a pretty long time and includes a 90-day hardware warranty (For the official Sim Pad Nano check Momokai.com)
Now if you're willing to spend $40-$50 on a keypad which is the typical price for a quality osu keypad I would choose some of the rapid trigger keypads coming out such as the Wooting UwU, the AlphaTec Helios, the FLUXPAD Keypad which was announced in the forums, or the Octa KPAD.
If you need links just DM me or something.