what's wrong with "off of"?
it has a long history, which, according to the oxford english dictionary, stretches back over 500 years...
c1450 in G. Müller Aus mittelengl. Medizintexten (1929) 116 Take a sponfull of e licour..of of e fyir and sette it in good place tyl at it be ny colde, soo as ou mayst suffryn to holdyn er-in in hand.
a1616 SHAKESPEARE Henry VI, Pt. 2 (1623) II. i. 98 A fall off of a Tree.
1667 A. MARVELL Corr. in Wks. (1875) II. 224 The Lords and we cannot yet get off of the difficultyes risen betwixt us.
1678 J. BUNYAN Pilgrim's Progress 49 About a furlong off of the Porters Lodge.
1712 R. STEELE Spectator No. 306. 6, I could not keep my Eyes off of her.
1720 D. DEFOE Mem. Cavalier 281, I had perswaded him off of that.
1748 S. RICHARDSON Clarissa V. xiii. 132 Biting my lip, [was to indicate] Get off of that, as fast as possible.
1775 P. OLIVER in T. Hutchinson's Diary 7 Dec. I. 581 A Rebell Pirate..taken..off of Cape Ann.
a1805 in F. J. Child Eng. & Sc. Pop. Ballads (1894) V. IX. 106/2 Aff o the weather he took the skin, An rowt his bonny lady in.
1824 J. WIGHT Mornings at Bow St. 21 Two young men..were charged by a watchman with having ‘bother'd him on his bate,’ and refused to ‘go along off of it when he tould 'em.’
1843 T. C. HALIBURTON Attaché 1st Ser. II. xii. 210 The groom has stole her oats, forgot to give her water, and let her make a supper sometimes off of her nasty, mouldy, filthy beddin'.
1868 HARTLEY Clock Alm. in Leeds Mercury Weekly Suppl. (1895) 5 Oct., He connot forshame To lift up his een off o' th' graand.
1875 P. BROOKS New Starts in Life viii. 129 If you could have filled his pockets with gold, and feasted his hunger off of silver dishes.
1909 G. GREIG Mains's Wooin' 6 He's swallowed the dictionar', min, an's tryin' to get 'er aff o's stammack.
a1922 T. S. ELIOT Waste Land Drafts (1971) 5 The reputation the place gets, off of a few barflies.
1962 F. NORMAN Guntz i. 15, I got hold of this very very old typewriter off of a friend of mine.
and, of course, withnail...
"excuse me, we were wondering if we could purchase a pheasant off of you".