Do you have the original project where the hex file for the CY8C5467AXI-LP108 build?
If so, it may be an easy recompile for the CY8C5868AXI-LP035. And yes: It does mean two hex files.
Even if you could change a few bytes inside the hex file to force the CY8C5868AXI-LP035 to be a valid target device you would by default creating a second hex file for this other PSoC5.
In general I don't recommend the target device alteration method I mentioned above. The primary reason is that there is a reason the target device is first checked before downloading into the target. Each IC might have different resources available and might have similar resources at different addresses. That's why it is highly recommended to perform the following steps:
Copy the original source project to a new project.
Change the target device on the new project.
Rebuild the new project.
Use this version of the hex file.
This guarantees that a successful build will fit into the new target PSoC and make sure the configuration gets compiled and linked to the correct resource addresses.
Len "Engineering is an Art. The Art of Compromise."