A familiar is not random and from what I've experienced, isn't something that can or should be summoned before it's ready to be part of your life.
When it's time to meet your familiar, it will come along. Be it a stray cat who won't leave your house, a stray dog following you around, an animal at the pound that you can't walk away from, a animal given to you by someone else, ect.
When it's time, it's time. Don't rush it or try to find a substitute. They are there to guide and aid us when our souls are ready to learn the lessons their souls teach us.
i got my familiar when i went to the pound. i was actually looking for a dog then i saw this black cat. i looked into her eyes and there was just something about her. she sat and stared at me for ages. so i took her home.i was told she never got on with anybody, but she does with me. its so wierd but it felt right that is should have her. just have patience. your familiar will come along.
my familiar is my cat. my family went to the pound to get my dogs registered and I went to look at the cats. there was this one cat who played with me when I stuck my finger in the cage and around other people he hid in the corner. we took him home that day. you cant summon a familiar you have to wait for it to come to you.