Try asking on vogons.org, they will have people that have experience replacing disks in Win2K systems.
Options I can see:
(1) Buy a CF card and a CF-to-IDE adaptor. CF cards natively speak IDE/PATA, the adaptor just re-arranges the wires and add a power connector.
Sadly CF cards are expensive and the cheap ones are probably just SD card adaptors with a chipset inside

But if cost isn't a problem then it would be worth trying in parallel to the SATA SSD option to see which one works best.
(2) Buy a mainline brand SATA SSD from a vendor in your country that specialises in computer parts and isn't known for greymarket fake shennaneggins. I'd go for a traditional 2.5" SSD form factor, not mSATA, just because of higher availability.
Good known brands: Samsung (makes their own flash), Sandisk (makes their own flash), Crucial. There are lots more but these are a starting point.
Also buy a few different models of SATA to IDE converter. Make sure they look different (ie different main chip and/or PCB layout) as the "law of packaging inertia" applies (if it looks the same then it is the same). These will be cheap compared to the disk itself and it would be worth trying a few.
Warning: I've had a SATA to USB that reduce the reported disk size slightly! Hopefully they don't do this any more. It meant that partitions went "past" the end of the disk when used, sending my kernel into conniptions. Since then I've always partitioned my disk a few MiB short of the end, just in case. I'm probably going to do that for the rest of my life now just because of that one bad experience *sigh*
Other thoughts:
(a) Does win2k have a maximum disk size limit?
(b) You probably don't need a more expensive SSD with RAM (most cheap SSDs are "dramless") unless your scope writes lots of data to disk all of the time. Even then it will still probably be fast enough compared to the original HDD?