The phrase "almost too small" is correct and usable in written English.
It can be used to describe something that is very close to being excessively small, often implying that it may not be suitable or adequate.
Example: "The dress was almost too small for her, but she decided to wear it anyway."
Alternatives: "nearly too tiny" or "practically too little".
A tiny gun, almost too small to be real.
Tenet's current quarters are almost too small to contain him; he is a large and perpetually restless man.
One robot arm endlessly forms three perfect bends in two connector wires and slips them into holes almost too small for the eye to see.
In one corner, printed in letters almost too small to see, is a poem credited to Netzahualcoyotl, the pre-Hispanic philosopher-king.
WHEELCHAIR ACCESS -- Everything is on one level, but the restroom is almost too small for a person, never mind a wheelchair.
This is the only copy of Jane Eyre that I have ever owned and the print size is now almost too small to read.
Readers with fading eyesight may wonder whether the savage migraines induced by the almost-too-small-for-comfort typeset are worth incurring just to read 200 more of Rob Fearn's words about the new album by Keane.
The star itself is almost certainly too small to appear as anything other than a point, and a planet should not be visible.
In volunteer and in animal model studies, the number of subjects is almost always too small to measure probabilities of infection at very low doses.
Those improvements, if they materialise and can be measured, will almost certainly be too small to impress new-economy zealots who foresaw a doubling or more of long-term growth.
"A Little Too Close to God," David Horovitz's cogent, impassioned and yet zestfully common-sensical report from the Israeli front, portrays a country not so much divided as multiplied against itself, where almost nothing seems too small to provoke a battle.
