Welcome to the forum, @Maryam_21!
I don't think the QIIME 2 team has the bandwidth to add another pre-trained classifier at this time, but here are a few different ways you might work around your memory challenges.
First, if any community members have already have a 341F/805R SILVA classifier they can share, that would be amazing!
If nothing turns up, you may be able to use RESCRIPt to build a custom classifier that does what you need. It offers a couple of different ways to filter and dereplicate the reference data while building an amplicon-specific database, which will in turn reduce memory requirements to build the classifier.
A colleague has been able to build amplicon-specific classifiers from SILVA with 16GB of RAM. If necessary, dropping species-level labels will help you reduce the size even more. If you can run the pre-trained v4 classifier locally, you probably have the resources to run your own custom v3v4 classifier.
If your hardware still isn't up to the task with RESCRIPt, you might consider using an institutional cluster, or renting a server for a short time (often surprisingly affordable). A 
search of this forum should turn up a few posts with server-rental resources.
Good luck!
CK