Many use standard 'Copper Slip', like Fenwick’s Copper Anti-Seize grease, but yes there are products more specifically marketed as Titanium 'anti seize'. Finish Line did a product called 'Ti Prep' that I can't see listed anymore but maybe still found somewhere as old/new stock, current products available include 'Park Tool ASC-1 Anti-Seize Compound', 'Fenwicks PTFE anti seize' and 'Silca Titanium-Optimised Anti-Seize Paste' to name just three that should be obtainable through a LBS as all are distributed by popular suppliers. I did try linking to the manufacturer or distributor for each item so if anyone was interested they could read more about each in detail; but couldn't get the link to work once published.
Personally if the seatpin fits well initially and can be moved easily then I'd always suggest removing on a yearly basis to make sure it stays that way and doesn't seize, especially on a bike used in all weathers with no mudguards. Note frames and seatpins can vary interms of the accuracy of listed size so pay attention to just how good the initial fit is, some may not be that tight and prone to slipping no matter how tight you do the up the clamp and vice versa others may be so tight they are difficult to move even when new; the former you'd expect to be less anxious about it seizing up than the latter of course.
As you will not need to use much these products should last years.