These lines create the dropdown:
Code:
<select id="po{$v.classid}" name="{$poname}"{if $disable} disabled="disabled"{/if}{if $nojs ne 'Y'} onchange="javascript: check_options();"{/if}>
{foreach from=$v.options item=o}
<option value="{$o.optionid}"{if $o.selected eq 'Y'} selected="selected"{/if}>{$o.option_name}{if $v.is_modifier eq 'Y' && $o.price_modifier ne 0} ({if $o.modifier_type ne '%'}{include file="currency.tpl" value=$o.price_modifier display_sign=1 plain_text_message=1}{else}{$o.price_modifier}%{/if}){/if}</option>
{/foreach}
Choose your favorite method to to change the font - font tags or a css class reference.