It is possible to use 3rd party SFP’s in a Cisco 3750 with the following commands:

Switch(config)#service unsupported-transceiver

and

Switch(config)#no errdisable detect cause gbic-invalid

The first command will generate the following warning from cisco :

” Warning: When Cisco determines that a fault or defect can be traced to
the use of third-party transceivers installed by a customer or reseller,
then, at Cisco’s discretion, Cisco may withhold support under warranty or
a Cisco support program. In the course of providing support for a Cisco
networking product Cisco may require that the end user install Cisco
transceivers if Cisco determines that removing third-party parts will
assist Cisco in diagnosing the cause of a support issue.”

I wouldn’t recommend using non-Cisco SFP’s in production environments, but for a lab save the bucks and go for it.