New program in user's portable computer requires administrator credentials.
When you say "new program", I hope you mean old program, but new to you. No new program should require admin rights unless it is changing the system. If it is new you need to discuss the design (or rather lack of) with the producer of the program.
If it is an old program, then what we did when I was paid to fix these problems was to make it work without admin rights. The tool of choice for doing this was Aaron Margosis' LUA Buglight. The last version was supposed to work with Windows 10. You will probably need a Windows10 system to run it.
Basically, what it does is to run without admin rights until it comes across an issue which it then deals with by using elevated rights, records what it had to do, and carries on until you close the program. So you need to know how to fully exercise the program, and to start on a system where your errant program has never been run. Then look at the results. They will suggest how to fix the old program. Mostly you can use application compatibility fixes. Sometimes you have to slacken permissions.
User will run program repeatedly, randomly, in field. No remote access availability.
Impermissible to divulge /reveal password.
Is there a way to submit password invisibly to program at each start?
It's possible that one of the options already suggested, or one of the programs designed to launch a runas equivalent with an obfuscated password will work. However, you need to check that using a different user account, which you will be doing, doesn't create it's own problems. For example, your unprivileged user may not be able to access data files created by the elevated program. Modern programs (badly designed) requiring admin rights may only work when the user is elevating themself.
If the elevated program is interactive and uses file open or save dialogs, then it's obviously extremely easy to open a command prompt with admin rights.
