The best software solution for self-service I’ve found over the years: http://www.r-studio.com/
If it’s beyond the scope of DIY, I have used Kroll Ontrack for customers several times since 2004 with excellent results. You will pay a small evaluation fee when you ship the drive to them and then they will come back with the details of the recovery possibilities and pricing. You can then determine whether the cost of the recovery is worth it. On a stand-alone external drive, it’s been between a few hundred dollars on up into the $1,500 range.
Every time I see someone lose data or have to pay a “ransom” to retrieve it from good companies like this, I’m reminded that 2 is 1 and 1 is none and that backups are not that expensive. Hope the DIY option works for you.