A few years ago I posted a submission for the portable version of the game streaming client, Moonlight:
viewtopic.php?p=93108#p93108
Since then, a replacement game streaming service, Sunshine, compatible with the Moonlight client, has been developed and has a portable version.
Sunshine project site: https://github.com/LizardByte/Sunshine
To download, go to the Releases section
https://github.com/LizardByte/Sunshine/releases
and download the sunshine-windows-portable.zip file. Extract to a folder of your choice, and double-click sunshine.exe to start the game streaming service.
Note: The Sunshine game streaming service and the NVIDIA game streaming service will conflict with each other if run at the same time. You can right-click on the Sunshine notification icon in the task bar to Open Sunshine configuration settings in a browser window and get instructions on how to resolve these conflicts.
To end the service, right-click on the Sunshine notification icon in the task bar and select Quit.