Grab you Yellow pages & find a mower repair shop, not a glass front retail outlet, you know, one where they actually make a living by fixing mowers.
Take you spindle housing to them and ask what they can sell you that can be made to fit.
This is what I do every day of the week, find parts that can be used to replace obsolete parts.
Do not expect a drop right in replacement, but usually I can find a part close enough to be made to work.
The other alternative is to go to a small engineering shop.
The kind of place when one person wanders around 20 machines on the floor & a second answers the phone & does the accounts.
A spindle housing is nothing more than a flanged tube with 2 bearings and a shaft running through it.
They are a simple fabrication, but remember you are paying for the skills of the machinist so don't expect it to be cheap.