Microsoft's Chinese IME is probably not your best choice.
搜狗's IME displays 辶
by typing chuo
.
The same is true of iOS's and OS's IMEs.
Radicials seem to have pinyin names as well, these pinyin in general should be able to type up the radicals: for example 讠
can also be typed up by inserting the pinyin yan
into any IME (Microsoft not included, probably).