I'm with Shaun on this one.
It may be a clever idea, but not my style.
There are entire books on the concept of reciprocity / gifting in sales. Personally, it turns me off. Bigtime.
If he's elusive, there's a reason, and throwing in a gift (for me) would backfire. If it's cheap, he'll know it, and if it's too nice, he'll feel obligated and resentful. Either way, he probably didn't wake up this morning thinking "wow I need a new watch" any more than I woke up thinking I need a timeshare presentation.
The gifting of the watch is an attempt to satisfy your needs, not his, and he'll know it. If he's a busy guy, you've just added yourself as one more thing for him to deal with.
My favorite salespeople are low key who let you know they are available if needed, but not pushy.
Sorry- but good luck anyway!