Synonym for "for the time being"
If you're asking if there's something now, I'd just say "at the moment".
https://www.merriam-webster.com/dictionary/at%20the%20moment
If you're saying that there is a short time where you are available, then I would be specific about when that period ends.
Eg
Are there any volunteering opportunities at the moment? I am available until the end of October 2020.
You might say the nonce. (M/W) has it as "for the time being" and "the ... present occasion, purpose, or use "