If you find the WHOLE board for a specific model of laptop on Ebay with the higher-clocked i7u variant, you can switch those out, but the performance difference for the cost it will probably run you probably isn't worth it.
There can be tons of issues with swapping out laptop chips, because they usually have OEM motherboards with only so many CPUs capable of running, let alone being supported. You have to do a lot of digging for answers to what supports what and things like that. Then you would have to actually find a way to get said processor, and who knows how much money it would take. It would be more trouble and/or money than it is worth.
There are several users are getting such kind of common upgradation issues in case of making an update on their Laptop. They can able to solve that particular errors by getting suggestions from [scam link removed] that will be helpful to repair those errors easily.
Which would be valid if you were able to swap those CPU's, but you can't.