Have you checked SeraCare materials, they have some of the common variants such as p.V617F (https://www.seracare.com/globalassets/seracare-resources/pi-0710-0408-seraseq-myeloid-mutation-dna-mix.pdf)

Similarly: https://horizondiscovery.com/en/reference-standards/products/jak2-v617f-reference-standard-50

Also you can always try to make a gBlock which IDT provides (https://www.idtdna.com/pages/products/genes-and-gene-fragments/double-stranded-dna-fragments/gblocks-gene-fragments).

Several cell lines carry a JAK2 V617F mutation, e.g.

MUTZ-8 https://www.cellosaurus.org/CVCL_2130

HEL https://www.cellosaurus.org/CVCL_0001

MB-02 https://www.cellosaurus.org/CVCL_7075

SET-2 https://www.cellosaurus.org/CVCL_2187

UKE-1 https://www.cellosaurus.org/CVCL_0104