What is your revenue target? There are a lot of different approaches depending on if you're looking to make a few hundred dollars to cover some nicer awards vs. several thousand dollars to cover your judges' travel and fees.
The most basic way to think about revenue is to review your entry and stall fees, and see if you have room to increase them based on how they compare with fees for similar events in your area.
What is the membership fee for your club, and is there a members vs. non-members rate for show entries? I would be working hard at the event to sign up non-members as new club members; maybe there's an on-site discount for entries or stalls if you become a member there. Or a credit towards the next show. Or a raffle to win a donated prize open to all new members who join that weekend (note that different states have different laws about who can run a raffle and how you can obtain a ticket).
Does the club do clinics or webinars? That could also be something where you offer tiered members vs. non-members rates, and promote that at the show. Or if the scheduling at the facility allows it, offer a clinic concurrently, or the day before or after the show. Here's a planning guide for hosting a clinic:
Equestrian Clinic Revenue Planner
I agree with
@ClearDonkey about sponsors, offer different levels for different contributions. This is our sponsorship overview for our local horsepark (the website desperately needs an update, but the info, including sponsorship rates, from 2020 is there):
Advertise your business at one of GMHA's top equestrian events - become a sponsor! A great way to improve your visibility while supporting GMHA.
www.gmhainc.org
Last year we started partnering with a local cafe to bring their food truck rather than running onsite concessions. The finances are much more favorable with the new arrangement. I'd reach out to local food trucks you like and ask what they typically pay to be onsite at a large event, and/or if their arrangement is typically profit sharing.
What is the arrangement with the show photographer? Do they pay a fee to be there? Share profits from photos sold?
In my experience, tack swaps take a ton of volunteer time & capacity for very little payoff. If you have a 4-H club or similar willing to organize and run it, then at least that takes care of the labor. You'd have to come up with a fair way to split any profits in return. I would expect the profits to be very small unless you're in a higher end area where people are willing to donate nice tack.
I'll stop there because other suggestions would be more labor intensive so really only worth it if your revenue targets are more robust.