Sure! Just navigate to their website, click "Tickets & Hospitality" in the header, and choose either "Buy Hospitality" or "Matchday VIP".
Cheapest you'll find probably run around 200-300 pounds/person. They get a lot more expensive from there. The various packages are detailed in there, but most include a meal before the game, a cheap souvenir, a drink after the game, etc. If you can swing it and you don't expect to attend a ton of Chelsea games on the regular, it can definitely be worth it for the experience- you do get more than just
a game ticket. On the lower end of the price spectrum the seats you'll get are in the West Stand Upper (upper deck, long side of the field at the Shed End) but there's really no awful seats at the Bridge. EDIT
: Actually looking at the offerings now, looks like the seat offerings are more spread out depending on which you choose- this is good. We did one of the packages (there were 6 of us) for Boxing Day in 2019 (an unfortunate loss to Southampton) and it was pretty swank.
Just to confirm I'm not talking out of my ass, my SIL has been a full time Chelsea employee for 6-7 years and my FIL is a season ticket holder. (I apologize but I can't really help with obtaining tickets). My SIL is up there in the Stadium Tours & Club Museum (shameless plug) hierarchy so if anyone ever has a hankering to tour the Bridge (it's actually a pretty cool stadium tour, as they go) let me know and I can most likely get you a discount/free tour.
: If you're not down with the whole hospitality thing and want to go the regular route- your best bet (at least with Chelsea, although I suspect this holds true for most big clubs) is to try for early round cup games against lower league opposition, or a group stage game against a European minnow. I went to a group stage Europa league game against PAOK a few years back and the stadium was only 3/4 full- that's something where you could just walk up to the ticket box at game time and buy a ticket. Those games are fairly rare though, and generally much earlier in the season (fall timeframe).