First of all, I commend you for posting in Relationship and Dating, most people now put their problems and indeed anything else in CB....so well done rowan.
Dave wasn't the first love of your life and he may not be the last.
Dave is dead........I am not suggesting that you forget him, as that just won't happen, but you now have to face the facts that you need male company and almost certainly...sex.
When you meet someone, please, do not compare him with Dave.....cus he wont be Dave and why should he.
Dating sites may well be the answer, but as mentioned above ...be careful, as you might meat the "wrong kind" whatever that may be.
I am not a fan of clubs, bridge club, gardening club.......possible.....but may take too long to meet someone.
Unless you are resigned and choose, do not go into old age....alone.
Good luck.