Italeri issued both the PzI ausf A and ausf B long ago. Relegated to the $5 table at hobby stores or model shows.
Tristar was out of production for a bit -- but are being relaunched under Hobby Boss. They might be a tad more difficult to find than DML but should still be plenty. Tristar also made a Pz I training vehicle too.
I agree that it's a toss up btn Tristar and DML.