Draw me, like one of your French girls...
You want something arty, unique, cool, but you don't want to break the bank or wait too long - I think you're looking for a drawing commission. There are multiple options available, the quickest and cheapest of which is a charcoal portrait from a (good quality) supplied photograph. At the other end of the scale for drawn commissions are pastel portraits from an initial live sitting, finished from a photograph. Any combination of photo/sitting/medium/materials can be available to suit the project and your budget.
Budget between £100 and £600 for something from this menu.
You've got a legacy in mind, a piece that will stand the test of time and look majestic in perpetuity. I think you're looking for a commission in oil paint. I'm happy working from a (good quality) supplied photograph, or from life, or using a combination of both. Lead times are a little longer than drawing but most projects should be finished within four to six weeks from initial sitting, subject to drying time.
There are a lot of options available in terms of materials (size, type etc) so budgeting is in a broad range starting at £600 and heading upwards depending on your choices.