The ability to offer actual money as a bounty is not currently implemented. Judging by [the feature request on Meta Stack Exchange](https://meta.stackexchange.com/q/25615/295684) (and [a duplicate thereof](https://meta.stackexchange.com/q/243404/295684) and [a similar one](https://meta.stackexchange.com/q/57850/295684)), it will likely not be added. The reasoning given for that decision was that introducing real cash as stakes would tremendously exacerbate the (usually) friendly and constructive competition we currently have into unhealthy money seeking. Additionally, it would likely demotivate the many answering users who give of their knowledge freely, thereby taking expert attention away from the question authors who do not have real money to spend.

If you would like to promote your question further, I would encourage you to write answers to other questions. Once you reach 200 reputation, you'll be able to place a bounty on that question again. In the meantime, if you run across any new relevant information or make any new attempts, make sure to edit it into your post; it might help a potential answer writer.