Reality check.
You have spindles that are old enough to both drink & vote.
So they have served you well.
Amortised over 23 years the cost per mow is less than a cup of bad coffee.
Modern spindles are a lot cheaper than the old ones in more ways than price.
However if you can not afford to fit original new one s try the aftermarket companies like Stens, Rotary, Oregon for an OEM replacement.
After that any spindle where the pulleys and the blades are the same distance off the deck as your old ones can be made to fit.
Just make sure you can get a pulley the same size for the top & blades the same length as your originals.
Also check the blade width & thickness, cheaper spindles take cheaper thinner blades