There's plenty of cheap ink for your printer on Amazon, here's a link of an example I found:

Uniwork Compatible Ink Cartridge Replacement for HP 564 564XL for Photosmart 6520 5520 4620 5510 C410a 6525 5514 OfficeJet 7510 4620 DeskJet 3522 Printer (4BK/2C/2M/2Y), 10 Packs https://www.amazon.com/dp/B07S3RZCC3/ref=cm_sw_r_cp_apa_i_wFU9DbGGDA7V3

Anyways, what is good about your printer is that since it doesn't have the print head build into the cartridges, buying third-party ink is extremely cheap compared to other cartridges, like HP 60, 61, 63, 64, 65.

Hope this helped.