Craigslist...
David Weaver
at any given time, because of the relatively low dollar value and high weight of those, they seem to be popular on CL rather than auction sites.
Out of curiosity, I checked my CL here, and there were four delta machines, but none with a part like yours that I could see (I followed your part number and found pictures of the part on various sites).
I guess the internet is a blessing and a curse for parts in that it gets us instant access to lists of parts, but in my experience, many of the sites seem to drop ship from the same place. You can test their competence by ordering a part and then requesting an update soon after or saying you'd like to cancel your order. They can't do it because they're just putting in an order somewhere to have the parts shipped to you. I've had that experience with appliances when a 3 day part turns into 20 days and nobody can tell you where the part is, then it shows up after you've "canceled" and the charge for it is reinstated unless you spend your own money to send it back.
Point being, there's probably only one or two places with all of those parts rather than many, and the ease in finding the parts means that folks with broken machines loot them pretty soon. I don't think my delta planer was more than about 3 years out of production when I found the blade retaining part to be absent everywhere.
Not surprisingly, spare knives were all over the place once people realized they had to junk their machines and couldn't use them.
That bracket looks large enough that it could be fabricated, possibly even repaired, but probably at a cost either way (in your time or someone else's) that it's not worthwhile. I noticed the parts list for the machine showed many discontinued parts. I have no greater idea than anyone else about a good long term strategy to buy a machine these days and be able to fix it for long. As far as I can tell, even with cars, manufacturers are only required (by law) to be able to source or find parts during the car's warranty period.
(one of the CL machines here has a non-working part with advice in the ad that the part is only $9 and is easy to replace. out of curiosity, I looked the part up - it's NLA. I'd speculate that the seller is aware of that based on the price
)