Kaspersky has a rescue CD, which is a bootable Linux environment; this ISO can be put on a USB, and, the infected system can run this alternate OS instead...
THis does not really meet the definition of 'portable', which really refers to a program that may be run from within Windows without installation.
Microsoft also offers bootable scanner media, do a search for Defender Offline at MS' website...
HitmanPro I think can be run once from USB without install, and is about as effective/famous as MalwareBytes....(If neither of those two spot anything, you are likely clean, or, better off to resort to a wipe/reload)
Try this battery:
RKill and/or RogueKiller
AdwCleaner
JRT
MBAM
HitmanPro
If still suffering malware afterwards, you will need a specialist/expert willing to spend a few hours searching, and convince him/her that makes more sense than the 30 minutes a wipe/reload will take
