I've kept written notes he has made in sessions. I don't think they were meant to be comforting as they are quite matter of fact, but the fact that he wrote them and handed them to me was enough for me to latch on to them. I also kept a tissue I took from the tissue box the time when I first cried in session. I have a bottle of perfume that I only use on the day I see him (wasn't a conscious decision, it just happened that way) and now I've come to associate the smell with him. I've kept all the emails too and read them when he's away and I need to feel connected. I also have a photo of him saved in a secret folder on my phone. it's a very, very high resolution one...I can basically see the pores on his face haha. That helps.
i wish i could have a voicemail so i could sometimes listen to his voice. I also wish I could capture the smell in his office. I find it comforting...I genuinely feel like it alters the chemistry of my brain.