GIMP can open animated gifs, you could try downscaling in there.
From the looks of it you don't fully respect the pixel resolution though, since you have "big" pixels moving at "actual" pixel resolution:
Here's a quick thing you can do: open GIMP, "open as layers", import the gif, then export. GIMP is more aggresive in its (lossless) compression so that shaves a few KiB. A slightly more aggressive approach is to also do "Filters > Animation > Unoptimize", then "Image > Mode > Indexed", picking an appropriate amount of max colors (I went with 255, to minimize loss), then
switch back "Image > Mode > RGB" (the only purpose of this transformation was to reduce the palette), then "Filters > Animation > Optimize (for GIF)". Then finally exporting the result. That takes off a full megabyte. Then there's the downscale option - I would suggest doing that in the paletted phase, so you don't re-introduce new colors that complicate your gif palette.
For the record: the downscaled and downscaled-then-upscaled versions (with reduced palette)