Hello Mike! It's been a busy week so I only now had a chance to respond.
We owned a 6200CD/75 so I have more experience with those than I would like. The 6200 series was one of the earliest Macs to have ATA drives instead of SCSI. The internal drive bus is ATA/IDE.
Even later PowerMacs would have required a SATA PCI adapter card. The 6200 does not have a PCI slot. It the old "LC PDS" slot. So no to the SATA option.
The last place I saw that still sold ATA/IDE hard drives was NewEgg.com, but I have not checked in several years.
I think the real question here is what do your need to do with the 6200? If you only need to access data files, you can remove the current ATA drive and connect it to a newer computer—Mac or Windows— using a universal drive adapter. This one works with ATA/IDE drive as well as SATA drives and includes the power supply required for 3.5 inch drives:
NewerTech Universal Drive Adapter USB Bare Drive Adapter
I can find no online sources of OS 7.5 that I would trust as far as I can throw a bison. For OS 9, you would need a full retail disk. That is required because the 6200 was one of the Macs using the "system enabler" scheme. Gray install/restore disks from another Mac usually will not work because they do not contain a universal set of enablers.
And I concur with Odawg132—burned system disks are about 98% hopeless for this.
Thrift shops that handle computer stuff are your best bet. A friend found me a full universal install set of v7.6 on floppies at a Salvation Army Store.
I am not trying to be a online naysayer but rather give an honest assessment here: I must disclose my deep-seated displeasure with the 6200. It was without a doubt the most troublesome Mac we even owned, and we've owned dozens since 1990.
The two greatest days in our 6200 lives were the day we got it, and the day I parted it out for recycling. In between, digital misery. Reinstalling the OS was as good as a calendar because it told us when a fortnight had passed!
Before spending too much money on this thing, I recommend you read this old article on the subject:
https://lowendmac.com/2014/power-mac-and-performa-x200-road-apples/
Ours was far slower than our even older PowerMac 6100/60. It was so bad it could not run Excel spreadsheets at all, the same sheets that were quite happy and speedy when opened on the 6100/60. In the long run, the complete 6100/60 system I bought used for $25 from a print services shop worked far better and longer than the 6200 that cost many times that. The only bits of the 6200 that survived were the monitor—not bad— and the 4X optical drive, which still serves in an 8100/100 that shipped with a sluggish 2x drive.
I will admit that it ran best when I maxed the RAM at 64MB. Anything less was glacial. And "best was still far behind the 6100/60.
Again I'm trying to be open and realistic here, so I hope you take this missive in the spirit of helping it is offered.
Regards,
Allam