function avia_remove_wc_currency_symbol( $currency_symbol, $currency ) {
if (is_single()) {
     $currency_symbol = 'USD $ ';
     return $currency_symbol;
} else {
	$currency_symbol = '$ ';
    return $currency_symbol;
}
}
add_filter('woocommerce_currency_symbol', 'avia_remove_wc_currency_symbol', 10, 2);