Hooked On Quack
REV`REND DR LUV
here's some basic amazon search results. you'll want to filter with more details like keyless start/etc. Looks like $30-40 for the fob.
https://www.amazon.com/s?k=key+fob&af={"vehicle":"2018-47-499-287--9--7-19741-------1"}&pd_rd_r=fdbc4da3-7d08-4291-ac02-7bf13f73b04a&pd_rd_w=aTxKx&pd_rd_wg=trtIJ&pf_rd_p=bec88bc8-d41e-4895-a8dc-a35e165b8995&pf_rd_r=9JMDM6JJS1BSFS91TQMK&pid=rfF7GZy&qid=1630509498&ref=sx_pf_dsk_mvftr
Then go here and find your local Batteries Plus. Looks like they have a programming fee of $69.99 for a 2018 Chevy Tahoe Premier key fob.
https://www.batteriesplus.com/
Ordered FOB, closest B+ is in Augusta..