The best way I've found blades is, first does the deck have a flat top? Meaning it's fabricated(welded) heavy steel and the mandrel assemblies(spindles) sit flat on the top of deck, not like smaller decks that have all kinds of humps/valleys by being stamped thinner steel. Think brush hog behind a tractor type deck, compared to push mower type deck.
This means you don't need special designed type of blades and can run just a good flat blade with high lift, without any problems.
Next, need to know the deck size. 48", 54", 60", 72" and so on.
Just for some info, I have a 60" deck on my Kut Kwick and I can actually run blades made for a 61" deck with no problem. But, one needs to look under the deck to determine if a slightly longer blade can be swung with no problems of hitting any other blade or deck metal sides and spindle shafts are long enough that blades don't hit the deck's underside top.
When I got my Kut Kwick (used) back in 2015, I called the company and about ****e my pants when I heard what they wanted for 3 blades. $80 apiece and 3 blades needed. OH, **** NO. I then first took one blade off deck to see if I could find any #s. luckly, the previously owner used some standard, locally found blades that only cost $60 for 3.
This is when I then measured the spindle that protrudes from the underside of deck. Found spindle is 5/8" which is one of the standard sizes, so I went looking for other blades to swap as backup.
Surprisingly found some flat style, hi-lift blades at a local farm & home supply store, but they had the Craftsman/Husqvarna "star" attachment and were made for a 61" deck. No problem as the center hole still measured 5/8", so they fit perfectly onto the spindle and bolt had large flat washer to get good firm hold onto the blade and deck was large enough underneath to handle the extra blade lengths without hitting each other or the deck in any way. I spun the blades by hand when all attached just to be sure. These blades only cost $30 for 3, but were also thinner and lighter weight.
Something to also consider when finding blades is the blade thickness that the factory uses to help determine what blade to go with. For my Kut Kwick, the factory designed the spindle assemblies and all other drive accessories to swing a 1/4"(.250") blade. I have replacement blades(3-sets) that run from thicknesses of .208", .220" and also .250". There is a 3-blade weight saving of almost 4 pounds between the lightest blades and the blades the factory designed for.
What using lighter blades also mean is that there's less load on the engine due to lighter blade weights, so the engine rpms will rev quicker, so throttle recovers easier in tough, thick grass and engine doesn't labor as much under the load.
Also, using lighter blades, I can not go through as large of saplings or brush that my mower was made to do, so that thought must be kept in mind as lighter blades can deflect and bend easier with lighter weight(thinner) blades if something is hit the blade wasn't designed to cut. My deck using factory weight .250" blades was made to cut/chop up to 1-1/2" saplings. Deck alone weighs around 400#s while whole machine weighs somewhere at the 1200# mark. Powered by only a 20hp ONAN engine.