Hi, Maverick. I've been wanting to play this myself, so I found the sheet music on this page:

http://tonyupton.tripod.com/gow/NielGowsLament.png

If you don't count the pickup notes, the song has 20 measures. These are some reasonable chords for those 20. Most measures have two chords, thus:

1. D D
2 A Bm
3. D A
4. D Bm
5. D D
6. A D
7. D Bm
8. D D
9 D A
10. Bm Em
11 A D
12 BM
13 D A
14 BM EM
15 D EM
16. A A?
17 D D
18 A D
19 D BM
20 BM BM

This is for conventional tuning, EADGBE.

A number of measures have pick-up notes at the end, and no chord goes with them, because they are usually skittering up the scale. The best thing to do with them is to allow the accompaniment to die tactfully away towards the end of the measure.

PS Apparently it's Niel, not Neil.