k-folds cross validation with conditional logistic regression

I have a matched-case control dataset that I'm using conditional
logistic regression (clogit in survival) to analyze.  I'm trying to
conduct k-folds cross validation on my top models but all of the
packages I can find (CVbinary in DAAG, KVX) won't work with clogit
models.  Is there any easy way to do this in R?