How do I attach my MEMS device to a PCB? I do not have access to a die bonding machine
If you're just talking about mounting the die for a one-off prototype, you can do that freehand with a vacuum tool or tweezers and a small dot of epoxy (silver epoxy is common due to heat transfer and the fact that it's conductive). This was how they did it back before the automated die attach machines. Yield isn't very good, but it works. Ask whoever the tech in charge of your wirebonding machine is for some help, if you don't have a die attach machine presumably they do this on a regular basis.

If you're talking about actually doing wire bonding after die attach, you obviously need a thermosonic gold wirebonding machine. If you don't have access to one, you'll need to get access to somewhere that does (such as a university) or pay somebody to do it for you.

Having a professional shop do both the die attach + wirebond process is relatively cheap - I have had a prototyping shop do it it for a lot charge of under $1000, and they were happy to do a few dozen prototypes for that lot charge. You're also guaranteed that they'll do both the attach and bond jobs correctly, so if something goes wrong you won't be second guessing your mounting job.

You probably already know this, but you should keep in mind that to do chip-on-board you need the appropriate PCB finish - either soft gold or preferably ENEPIG, and the plating will need to be a certain minimum thickness for the bonding process.