So going on what you have said - definitely the SuperX 2017-2019 model with KP454 headset.
Complete 1 1/8 to 1.5" headset for SuperX 2017-2019(Cannondale part number KP454)
Head Tube UPR: 1 -1/2 in, LWR: 1 -1/2 in
Stock available @ list price £44.99 + free postage (https://www.cannondalespares.com/)
Lower Si to 1.5" bearing
Upper headset reducer cup
Upper headset bearing
23mm tall carbon fiber conical spacer
Upper bearing wedge
Actually seems surprisingly cheap for quite a comprehensive kit. The fact that everyone is selling them maybe suggests they fail a lot. I have seen complaints about rusting SuperX headset bearings - looks like original part is low spec (that is definitely proven true of other Cannondale bearings). and you could benefit from a stainless upgrade or better seals. On the other hand the originals may have just suffered from ingress of salt water or ferrous contamination, which will rust even many grades of stainless over time, or poor maintenance such as jetwashing and solvent application washing out the grease.
So if you want bearings only of the same standard as originally fitted then I would expect them to come in at £20-25 the pair for economy items, so potential savings are limited to maybe £20 over just buying a complete replacement.
As suggested, if there are markings on the originals that would make life easy. I can’t find any direct Cannondale info which shows which bearings are common across model ranges. The entire headset assembly is clearly unique as it includes the cap, bung etc. but the top and bottom race are definitely used in multiple models. In the absence of markings, measurement would provide confirmation.
Bearing measurement guide:
Enduro do a range of products focused on the bicycle market and get great reviews. Widely available from many suppliers (both bearings dealers and bicycle component dealers.
Their stainless items have lifetime no-corrosion guarantee. They do ceramic for some products but I don’t think there is a requirement in headsets. Stainless are typically approx. double the price of standard bearings.
I haven’t seen any clear info on the upper 1 1/8" bearing. I did see some people claiming that the lower 1.5" bearing is the B543 - 40x50x7 non-stainless the same as used in KP205 (Tapered Headset 1 1/8" - 1.5" Jekyll and RZ 120 frames) and KP119 HDL008 Headshock headsets. A whole KP119 headset is available for around £27 with 2x 1.5" bearings but these are a 90/90 deg (non-angular) so you would have to measure/check if this is what is fitted to the lower in your SuperX. In photos of the KP454 the bearings look angular to me. It was also claimed that the lower bearing is pressed into the headset (interference fit) in SuperX-2019 and to remove/replace requires an extractor/press tool (or careful use of a drift). The upper bearing was said to fit normally (slip fit).