I posted this deal a few months ago for a Datacolor SpyderX Pro, and some of the feedback was that the X-Rite i1 Display Pro was overall a better product (although more expensive). I noticed with the digiDIRECT 20% off sale on eBay, it's currently available for $319.20 using the DIGID20 code. Normal price on the non-eBay digiDIRECT website is $399 (currently $359.10 with their 10% off for Click Frenzy), and not too far off cheapest price on Camel which is $306.05.
Note, this is the Pro, not the Pro Plus. From what I gather the difference is that the Pro Plus is able to handle high brightness (up to 2000 nits) and high contrast (e.g. OLED displays), whereas the Pro is more for standard IPS monitors.
(If you're only likely to need this very occasionally, my previous post has some comments suggesting hiring one for a day or two, which is likely to be about $40/day (based on CGRentals, for the Pro Plus). If you plan on using it repeatedly, this seems like a good price for a good product.)
Part of the digiDirect eBay 20% off sale:
https://www.ebay.com.au/e/coupon-offers/20-off-digidirect-no…
There needs to be somewhere to rent these things. I only need them once every few years!