At 6 foot you're probably going to be looking at 150mm of drop. And thanks to the usual modern bike thing drops come in a wide range so not being aware you might struggle as to which size to get.
As droppers are an offroad thing, it would be usual to get as large a drop fits on the bike- and there many opt for about 175mm or even 200mm, but because your need is just to get the leg over(oo-er) pretty much anything that brings it down is going to be a bonus.
Next problem is money. And yet again, the in thing and pretty much something you cant do without offroad is priced accordingly. Popular = expensive, but there are some cheaper options, plus given the bike industry is going through a transitional period currently with some even big big companies are cutting back to the point they're in administration.
So you need a drop thats going to help say 150mm, but as said pretty much anything it going to be a big help, and when you get to the lower drop lengths, its there we can see the bigger savings.
I recently bought a high end dropper for a new build, which retails at over £300, for less than half price. My needs are similar to yours, as in it makes getting on the bike way easier, but not for the same reasons, as in mine arent medical, but i find it a real plus point getting on what I use as a commuting/shopping type bike as fully loaded with shopping, leaning it to such an extent to get the leg over(oo-er) makes it a bit unbalanced.
** IMPORTANT
One important thing to take note of is some droppers are internally wired through the frame and some are externally routed onto the frame(zip ties etc. I strongly suggest you look only for externally routed posts as those are going to be the easiest to fit and thus considerably hassle
Raleigh bikes make one called the RSP Plummet which retails around about the 50 quid mark. Its certainly cheap, and maybe not as robust as other higher priced, but its a good starting point for you to get on with and comes with a remote lever which many of the very highly priced ones do not so deffo a bonus there.
Not sure if 'Plummet' is such an ideal name but there you go.
#This post has the externally cable routing option
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Another brand which usually costs a bit less is one called 'Brand X' not the best name but it has a strong reputation amongst the MTB community as being of good quality, and so plenty I know use them. They aint no fox factory transfer or AXS, but they do the job and apparently so do it pretty well, and therefore should be an excellent choice for yourself.
Bit of a sale on in places and you should get a brand x in say 150mm drop for about 90 quid
#Brand x have an externally routed cable option on some of their posts to take note when ordering.
Buy your Brand-X Ascend II External Dropper Seatpost from our Dropper Seatposts range at CRC. £29.99. Free delivery available.
www.chainreactioncycles.com
If you think you need longer, theres a 170mm brand X here for about £100
Buy your Brand-X Ascend II XL External Dropper Seatpost from our Dropper Seatposts range at CRC. £49.99. Free delivery available.
www.chainreactioncycles.com