You are like so many other patients who like fuller or more shapely lips but don't want the expense and pain and downtime involved with keeping up the temporary fillers. A permanent lip implant is your best bet at a cost of roughly $1500-2000 per lip.
There are 3 major types of implants available and each with their own advantages. Atrium Advanta has been around longest and is a ePTFE gortex type implant that looks like a spaghetti noodle and is soft like a marshmallow. It gives a beautiful border ridge to the lip for great definition and can give some volume as well. It is the easiest to put in. Verafill or Fullfill is a saline filled implant that is amazingly soft due to the fluid inside the implant and gives great volume enhancement to the lips. Surgisil's perma facial implant is the latest to come out and is a silicone implant that looks and feels like a tapered gummy bear. It gives nice volume and definition but is not quite as soft as the other 2 but usually soft enough for most patients.
All three are placed into your lips quite easily under local anesthesia only. You can drive yourself home and expect some bruising and swelling for about 5 days. You will need antibiotic and antiviral pills for a week to 10 days so no infections erupt. The final results are seen about 2 months later although you look pretty good at 1-2 weeks. They are definitely worth it. They are easy to put in and easy to remove if you ever want them removed but most never do since they love the look.
Fat injections and silicone injections each have enough problems that very few docs do them anymore. Surgical rearrangements also have scarring and sensitivity issues so they also are not the best options anymore.