[Fizzlemizz]

I don't think it will achieve exactly what you want, which would probably require custom textures, but something l ike:

local backdrop = {
	edgeFile = "Interface\\Tooltips\\UI-Tooltip-Border",
	edgeSize = 3,
	insets = {
		left = 0,
		right = 0,
		top = 0,
		bottom = 0,
	}
}
_G[self:GetName().."ScrollBarScrollUpButton"]:SetBackdrop(backdrop)
_G[self:GetName().."ScrollBarScrollUpButton"]:GetNormalTexture():SetTexCoord(-0.0015, 1.0015, -0.0015, 1.0015)
_G[self:GetName().."ScrollBarScrollUpButton"]:GetPushedTexture():SetTexCoord(-0.0015, 1.0015, -0.0015, 1.0015)
_G[self:GetName().."ScrollBarScrollUpButton"]:GetDisabledTexture():SetTexCoord(-0.0015, 1.0015, -0.0015, 1.0015)
_G[self:GetName().."ScrollBarScrollUpButton"]:GetHighlightTexture():SetTexCoord(-0.0015, 1.0015, -0.0015, 1.0015)