"convocation for" is correct and usable in written English.
You can use it when referring to a gathering or meeting, often one called together for a particular purpose. For example, "The mayor has called a convocation for all members of the city council."
"Convocation for a Bicentennial," Harvard Magazine, September 9, 2016.
In May 1536 Pope Paul published a bull of convocation for his proposed council to be held in Mantua.
June 24th 1944 – Special Convocation for the Navy V-12 Unit was held on front campus.
The governor was scheduled to speak at 3 p.m. today at a convocation for about 550 master's degree candidates at Teachers College, an affiliate of Columbia University.
22 W Convocation for new students at 11 a.m.
This is an edited version of the address delivered at the August convocation for new undergraduate students.
Representatives of a nation may boycott international conferences or convocations, for example, as a means of indicating disapproval of another nation's political policy or conduct.
These mosques generally hold the periodic, smaller scale convocations for neighbourhood members.
Maduro's response included a call for convocation of a constituent assembly to draft a new constitution, an action many of his opponents viewed as yet another authoritarian power grab.
She was delivering the convocation address for first-year students, a longstanding tradition, for which I was given a front-row seat in the university's enormous chapel.
A convocation event for 122 graduating students serenaded with arias by Italian tenor Andrea Bocelli - flown in at a reported cost of £1m - and our own Royal Philharmonic concert orchestra, interrupted only by the evening call to prayer.
