You can install Shoulder Eye Bolts seeing you don't have tie down points.
This page shows their ratings. Many different brands online.
https://www.certifiedslings.com/load-limits/shoulder-eye-bolts-a-swivel-hoist-rings/
You really want a straight or inline pull on these so would install them on the inside edges of your trailer. Hopefully that makes sense.
If you use straps you need to make sure that none of the strap goes over a sharp edge. I'm sure people get away with this but it's usually in manufacturers specs/instructions.
Also hooks can and do slide along metal if they aren't wrapped around something to stop this travel.
Have you gone with your trailer to a local trailer shop? I'd be surprised if they didn't stock these or something similar to help owners in this situation. Or have a welder on site who is qualified to weld on tie down points.
But if you have a drill you could install yourself. You want to make sure there is enough material(metal) around the bolt.
https://www.homedepot.com/p/The-Hil...in-Shoulder-Pattern-1-Pack-320610-0/203809948
2 at front of trailer 2 at back. Or 3 at each end if you add safety chain.
I would use grade 8 nuts and washers.
As well as using 4 straps when I tow cars I also use a chain and binder at each end. It's cheap insurance.
https://www.homedepot.com/p/KingCha...-Safe-Work-Load-Storage-Pail-427490/304079339
You need to measure if it will work with your set up but you can get home depot or lowes to cut this chain in half. They then sell rated hooks for the ends that bolt on. I got snap hooks.
Then purchase binders to suit.
A local trailer shop will carry all these items but you may pay more than purchasing it yourself. But it will also give some piece of mind.
I'm not a professional tow truck driver and this doesn't constitute professional advice.